Venturi

ABSTRACT

A venturi is disclosed, the venturi comprising a mixing cavity surrounded circumferentially by an annular venturi wall, and a swirler having a plurality of vanes arranged circumferentially around a swirler axis, wherein the swirler and the annular venturi wall have a unitary construction. In another exemplary embodiment the venturi comprises an annular venturi wall, a swirler located at an axially forward portion of the venturi, the swirler having a plurality of vanes arranged circumferentially around a swirler axis, and a heat shield located axially aft from the swirler, wherein the annular venturi wall, the swirler and the heat shield have a unitary construction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application claims priority to U.S. Provisional Application Ser.No. 61/044,116, filed Apr. 11, 2008, which is herein incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates generally to venturis, and more specifically tounitary venturis having swirlers for promoting mixing of fuel and airand a heat shield for protection from combustion heat in fuel nozzlesused in gas turbine engines.

Turbine engines typically include a plurality of fuel nozzles forsupplying fuel to the combustor in the engine. The fuel is introduced atthe front end of a burner in a highly atomized spray from a fuel nozzle.Compressed air flows around the fuel nozzle and mixes with the fuel toform a fuel-air mixture, which is ignited by the burner. Because oflimited fuel pressure availability and a wide range of required fuelflow, many fuel injectors include pilot and main nozzles, with only thepilot nozzles being used during start-up, and both nozzles being usedduring higher power operation. The flow to the main nozzles is reducedor stopped during start-up and lower power operation. Such injectors canbe more efficient and cleaner-burning than single nozzle fuel injectors,as the fuel flow can be more accurately controlled and the fuel spraymore accurately directed for the particular combustor requirement. Thepilot and main nozzles can be contained within the same nozzle assemblyor can be supported in separate nozzle assemblies. These dual nozzlefuel injectors can also be constructed to allow further control of thefuel for dual combustors, providing even greater fuel efficiency andreduction of harmful emissions. The temperature of the ignited fuel-airmixture can reach an excess of 3500° F. (1920° C.). It is thereforeimportant that the fuel supply conduits, flow passages and distributionsystems are substantially leak free and are protected from the flamesand heat.

Various governmental regulatory bodies have established emission limitsfor acceptable levels of unburned hydrocarbons (HC), carbon monoxide(CO), and oxides of nitrogen (NOx), which have been identified as theprimary contributors to the generation of undesirable atmosphericconditions. Therefore, different combustor designs have been developedto meet those criteria. For example, one way in which the problem ofminimizing the emission of undesirable gas turbine engine combustionproducts has been attacked is the provision of staged combustion. Inthat arrangement, a combustor is provided in which a first stage burneris utilized for low speed and low power conditions to more closelycontrol the character of the combustion products. A combination of firststage and second stage burners is provided for higher power outletconditions while attempting to maintain the combustion products withinthe emissions limits. It will be appreciated that balancing theoperation of the first and second stage burners to allow efficientthermal operation of the engine, while simultaneously minimizing theproduction of undesirable combustion products, is difficult to achieve.In that regard, operating at low combustion temperatures to lower theemissions of NOx, can also result in incomplete or partially incompletecombustion, which can lead to the production of excessive amounts of HCand CO, in addition to producing lower power output and lower thermalefficiency. High combustion temperature, on the other hand, althoughimproving thermal efficiency and lowering the amount of HC and CO, oftenresults in a higher output of NOx. In the art, one of the ways in whichproduction of undesirable combustion product components in gas turbineengine combustors is minimized over the engine operating regime is byusing a staged combustion system using primary and secondary fuelinjection ports.

Another way that has been proposed to minimize the production of thoseundesirable combustion product components is to provide for moreeffective intermixing of the injected fuel and the combustion air. Inthat regard, numerous swirlers, mixer designs and venturi designs havebeen proposed over the years to improve the mixing of the fuel and air.In this way, burning occurs uniformly over the entire mixture andreduces the level of HC and CO that result from incomplete combustion.However, there is still a need to minimize the production of undesirablecombustion products over a wide range of engine operation conditions.Better mixing of fuel and air in fuel nozzles using swirlers in aventuri designed to promote such mixing will be useful in reducingundesirable combustion emissions.

Over time, continued exposure to high temperatures during turbine engineoperations may induce thermal gradients and stresses in the conduits andfuel nozzles which may damage the conduits or fuel nozzle and mayadversely affect their operation. For example, thermal gradients maycause fuel flow reductions in the conduits and may lead to excessivefuel maldistribution within the turbine engine. Exposure of fuel flowingthrough the conduits and orifices in a fuel nozzle to high temperaturesmay lead to coking of the fuel and lead to blockages and non-uniformflow. To provide low emissions, modern fuel nozzles require numerous,complicated internal air and fuel circuits to create multiple, separateflame zones. Fuel circuits may require heat shields from the internalair to prevent coking, and certain tip areas may have to be cooled andshielded from combustion gases. Additional features may have to beprovided in the heat shields to promote heat transfer and cooling.Furthermore, over time, continued operation with damaged fuel nozzlesmay result in decreased turbine efficiency, turbine component distress,and/or reduced engine exhaust gas temperature margin.

Improving the life cycle of fuel nozzles installed within the turbineengine may extend the longevity of the turbine engine. Known fuelnozzles include a delivery system, a mixing system, and a supportsystem. The delivery system comprising conduits for transporting fluidsdelivers fuel to the turbine engine and is supported, and is shieldedwithin the turbine engine, by the support system. More specifically,known support systems surround the delivery system, and as such aresubjected to higher temperatures and have higher operating temperaturesthan delivery systems which are cooled by fluid flowing through the fuelnozzle. It may be possible to reduce the thermal stresses in theconduits and fuel nozzles by configuring their external and internalcontours and thicknesses.

Air-fuel mixers have swirler assemblies that swirl the air passingthrough them to promote mixing of air with fuel prior to combustion. Theswirler assemblies used in the combustors may be complex structureshaving axial, radial or conical swirlers or a combination of them. Inthe past, conventional manufacturing methods have been used to fabricatemixers having separate venturi and swirler components that are assembledor joined together using known methods to form assemblies. For example,in some mixers with complex vanes, individual vanes are first machinedand then brazed into an assembly. Investment casting methods have beenused in the past in producing some combustor swirlers. Other swirlersand venturis have been machined from raw stock. Electro-dischargemachining (EDM) has been used as a means of machining the vanes inconventional fuel nozzle components.

Conventional gas turbine engine components such as, for example, fuelnozzles and their associated swirlers, conduits, distribution systems,venturis and mixing systems are generally expensive to fabricate and/orrepair because the conventional fuel nozzle designs having complexswirlers, conduits and distribution circuits and venturis fortransporting, distributing and mixing fuel with air include a complexassembly and joining of more than thirty components. More specifically,the use of braze joints can increase the time needed to fabricate suchcomponents and can also complicate the fabrication process for any ofseveral reasons, including: the need for an adequate region to allow forbraze alloy placement; the need for minimizing unwanted braze alloyflow; the need for an acceptable inspection technique to verify brazequality; and, the necessity of having several braze alloys available inorder to prevent the re-melting of previous braze joints. Moreover,numerous braze joints may result in several braze runs, which may weakenthe parent material of the component. The presence of numerous brazejoints can undesirably increase the weight and manufacturing cost of thecomponent.

Accordingly, it would be desirable to have a venturi having complexgeometries for mixing fuel and air in fuel nozzles while protecting thestructures from heat for reducing undesirable effects from thermalexposure described earlier. It is desirable to have venturis havingintegral heat shields having features that promote heat exchange andcooling of structures. It is desirable to have a venturi having complexgeometries with a unitary construction to reduce the cost and for easeof assembly as well as providing protection from adverse thermalenvironment. It is desirable to have a method of manufacturing toprovide a unitary construction for a venturi having complexthree-dimensional geometries, such as, for example, a venturi withswirler and heat shield systems for use in fuel nozzles.

BRIEF DESCRIPTION OF THE INVENTION

The above-mentioned need or needs may be met by exemplary embodimentswhich provide a venturi comprising a mixing cavity surroundedcircumferentially by an annular venturi wall, and a swirler having aplurality of vanes arranged circumferentially around a swirler axis,wherein the swirler and the annular venturi wall have a unitaryconstruction.

In another exemplary embodiment, the venturi comprises an annularventuri wall, a swirler located at an axially forward portion of theventuri, the swirler having a plurality of vanes arrangedcircumferentially around a swirler axis, and a heat shield locatedaxially aft from the swirler, wherein the annular venturi wall, theswirler and the heat shield have a unitary construction.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the concluding part of thespecification. The invention, however, may be best understood byreference to the following description taken in conjunction with theaccompanying drawing figures in which:

FIG. 1 is a diagrammatic view of a high bypass turbofan gas turbineengine comprising an exemplary fuel nozzle having a venturi according toan exemplary embodiment of the present invention.

FIG. 2 is an isometric view of an exemplary fuel nozzle having a venturiaccording to an exemplary embodiment of the present invention.

FIG. 3 is an axial cross-sectional view of an exemplary nozzle tipassembly of the exemplary fuel nozzle shown in FIG. 2.

FIG. 4 is an isometric view of a venturi according to an exemplaryembodiment of the present invention.

FIG. 5 is an axial cross sectional view of the exemplary venturi shownin FIG. 4.

FIG. 6 is another isometric view of the exemplary venturi shown in FIG.4, with a portion of the venturi sectioned away.

FIG. 7 is a top plan view of a venturi shown in FIG. 6 with a portion ofthe venturi sectioned away.

FIG. 8 is an isometric view of a venturi according to an alternativeexemplary embodiment of the present invention with a portion sectionedaway.

FIG. 9 is a flow chart showing an exemplary embodiment of a method forfabricating a unitary venturi.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in detail, wherein identical numeralsindicate the same elements throughout the figures, FIG. 1 shows indiagrammatic form an exemplary gas turbine engine 10 (high bypass type)incorporating an exemplary fuel nozzle 100 having an exemplaryembodiment of a venturi (such as items 500, shown in the figures anddescribed herein) used for promoting mixing of air with the fuel in thefuel nozzle 100. The exemplary gas turbine engine 10 has an axialcenterline axis 12 therethrough for reference purposes. Engine 10preferably includes a core gas turbine engine generally identified bynumeral 14 and a fan section 16 positioned upstream thereof. Core engine14 typically includes a generally tubular outer casing 18 that definesan annular inlet 20. Outer casing 18 further encloses and supports abooster 22 for raising the pressure of the air that enters core engine14 to a first pressure level. A high pressure, multi-stage, axial-flowcompressor 24 receives pressurized air from booster 22 and furtherincreases the pressure of the air. The pressurized air flows to acombustor 26, where fuel is injected into the pressurized air stream andignited to raise the temperature and energy level of the pressurizedair. The high energy combustion products flow from combustor 26 to afirst (high pressure) turbine 28 for driving the high pressurecompressor 24 through a first (high pressure) drive shaft 30, and thento a second (low pressure) turbine 32 for driving booster 22 and fansection 16 through a second (low pressure) drive shaft 34 that iscoaxial with first drive shaft 30. After driving each of turbines 28 and32, the combustion products leave core engine 14 through an exhaustnozzle 36 to provide at least a portion of the jet propulsive thrust ofthe engine 10.

Fan section 16 includes a rotatable, axial-flow fan rotor 38 that issurrounded by an annular fan casing 40. It will be appreciated that fancasing 40 is supported from core engine 14 by a plurality ofsubstantially radially-extending, circumferentially-spaced outlet guidevanes 42. In this way, fan casing 40 encloses fan rotor 38 and fan rotorblades 44. Downstream section 46 of fan casing 40 extends over an outerportion of core engine 14 to define a secondary, or bypass, airflowconduit 48 that provides additional jet propulsive thrust.

From a flow standpoint, it will be appreciated that an initial airflow,represented by arrow 50, enters gas turbine engine 10 through an inlet52 to fan casing 40. Air flow 50 passes through fan blades 44 and splitsinto a first compressed air flow (represented by arrow 54) that movesthrough conduit 48 and a second compressed air flow (represented byarrow 56) which enters booster 22.

The pressure of second compressed air flow 56 is increased and entershigh pressure compressor 24, as represented by arrow 58. After mixingwith fuel and being combusted in combustor 26, combustion products 60exit combustor 26 and flow through first turbine 28. Combustion products60 then flow through second turbine 32 and exit exhaust nozzle 36 toprovide at least a portion of the thrust for gas turbine engine 10.

The combustor 26 includes an annular combustion chamber 62 that iscoaxial with longitudinal axis 12, as well as an inlet 64 and an outlet66. As noted above, combustor 26 receives an annular stream ofpressurized air from a high pressure compressor discharge outlet 69. Aportion of this compressor discharge air (“CDP” air) identified by thenumeral 190 in the figures herein, flows into a mixer (not shown). Fuelis injected from a fuel nozzle tip assembly to mix with the air and forma fuel-air mixture that is provided to combustion chamber 62 forcombustion. Ignition of the fuel-air mixture is accomplished by asuitable igniter, and the resulting combustion gases 60 flow in an axialdirection toward and into an annular, first stage turbine nozzle 72.Nozzle 72 is defined by an annular flow channel that includes aplurality of radially-extending, circumferentially-spaced nozzle vanes74 that turn the gases so that they flow angularly and impinge upon thefirst stage turbine blades of first turbine 28. As shown in FIG. 1,first turbine 28 preferably rotates high pressure compressor 24 viafirst drive shaft 30. Low pressure turbine 32 preferably drives booster24 and fan rotor 38 via second drive shaft 34.

Combustion chamber 62 is housed within engine outer casing 18. Fuel issupplied into the combustion chamber by fuel nozzles 100, such as forexample shown in FIGS. 2 and 3. Liquid fuel is transported throughconduits within a stem 103, such as, for example, shown in FIG. 3, tothe fuel nozzle tip assembly 68. Conduits that have a unitaryconstruction may be used for transporting the liquid fuel into the fuelnozzle tip assembly 68 of the fuel nozzles 100. The fuel supplyconduits, may be located within the stem 103 and coupled to a fueldistributor tip 180. Pilot fuel and main fuel are sprayed into thecombustor 26 by fuel nozzle tip assemblies 68, such as for example,shown in FIGS. 2 and 3. During operation of the turbine engine,initially, pilot fuel is supplied through a pilot fuel flow passage,such as, for example, shown as items 102, 104 in FIG. 3, duringpre-determined engine operation conditions, such as during startup andidle operations. The pilot fuel is discharged from fuel distributor tip180 through the pilot fuel outlet 162. When additional power isdemanded, main fuel is supplied through main fuel passageways 105 (seeFIG. 3) and the main fuel is sprayed using the main fuel outlets 165.

FIGS. 3-7 show an exemplary embodiment of the present invention of aunitary venturi 500. FIGS. 2 and 3 show an exemplary embodiment of afuel nozzle 100 and fuel nozzle tip 68 having the exemplary unitaryventuri 500. FIG. 8 shows an alternative exemplary embodiment of aunitary venturi 600. The term “unitary” is used in this application todenote that the associated component, such as the venturi 500, 600described herein, is made as a single piece during manufacturing. Thus,a unitary component has a monolithic construction for the component.FIG. 4 shows an isometric view of a unitary venturi 500 according to anexemplary embodiment of the present invention. The exemplary venturis500, 600 shown in FIGS. 3-8 include a circumferential array of vanes 508that impart a swirling motion to the air passing therethrough to enhancefuel-air mixing within the fuel nozzle. The exemplary venturis 500, 600shown in FIGS. 3-8 may have a unitary construction made using methodsdescribed subsequently herein.

Referring to FIGS. 2 and 3, fuel distributor tip 180 extends from thestem 103 such that main fuel passageways 105 and the pilot fuelpassageways 102, 104 in the unitary distributor ring 171 are coupled inflow communication corresponding fuel supply conduits contained withinthe stem 103. Main fuel passageways 105 are coupled in flowcommunication to main fuel circuits defined within unitary distributorring 171. Primary pilot passage 102 and secondary pilot passage 104 arecoupled in flow communication with corresponding pilot injectorspositioned radially inward within a fuel nozzle (see FIG. 3). It will beapparent to those skilled in the art that although the distributor ring171 has been described herein above as a unitary conduit (i.e., having aunitary construction), it is possible to use a distributor ring 171having other suitable manufacturing constructs using methods known inthe art. The unitary distributor ring 171 is attached to the stem 103using conventional attachment means such as brazing. Alternatively, theunitary distributor ring 171 and the stem 103 may be made by rapidmanufacturing methods such as for example, direct laser metal sintering,described herein.

FIG. 3 shows an axial cross section of an exemplary fuel nozzle tip 68having an exemplary embodiment of the present invention of a unitaryventuri 500. The exemplary fuel nozzle tip 68 shown in FIG. 3 has twopilot fuel flow passages, referred to herein as a primary pilot flowpassage 102 and a secondary pilot flow passage 104. Referring to FIG. 3,the fuel from the primary pilot flow passage 102 exits the fuel nozzlethrough a primary pilot fuel injector 163 and the fuel from thesecondary pilot flow passage 104 exits the fuel nozzle through asecondary pilot fuel injector 167. The primary pilot flow passage 102 inthe distributor ring 171 is in flow communication with a correspondingpilot primary passage in the supply conduit contained within the stem103 (see FIG. 2). Similarly, the secondary pilot flow passage 104 in thedistributor ring 171 is in flow communication with a corresponding pilotsecondary passage in the supply conduit contained within the stem 103.

As described previously, fuel nozzles, such as those used in gas turbineengines, are subject to high temperatures. Such exposure to hightemperatures may, in some cases, result in fuel coking and blockage inthe fuel passages, such as for example, the exit passage 164. One way tomitigate the fuel coking and/or blockage in the distributor ring 171 isby using heat shields to protect the passages (such as items 102, 104,105 shown in FIG. 3) from the adverse thermal environment. In theexemplary embodiment shown in FIG. 3, the fuel conduits 102, 104, 105are protected by gaps 116 and heat shields that at least partiallysurround these conduits. The gap 116 provides protection to the fuelpassages by providing insulation from adverse thermal environment. Inthe exemplary embodiment shown, the insulation gaps 116 have widthsbetween about 0.015 inches and 0.025 inches. The heat shields, such asthose described herein, can be made from any suitable material withability to withstand high temperature, such as, for example, cobaltbased alloys and nickel based alloys commonly used in gas turbineengines. In exemplary embodiment shown in FIG. 3, the distributor ring171 has a unitary construction wherein the distributor ring 171, theflow passages 102, 104, 105, the fuel outlets 165, the heat shields andthe gaps 116 are formed such that they have a monolithic construction.

FIG. 4 shows an isometric view of a swirler 500 according to anexemplary embodiment of the present invention and FIG. 5 shows an axialcross sectional view of the exemplary venturi shown in FIG. 4. Referringto FIG. 5, the exemplary venturi 500 comprises an annular venturi wall502 around the swirler axis 11 that forms a mixing cavity 550 wherein aportion of air and fuel are mixed. The annular venturi wall may have anysuitable shape in the axial and circumferential directions. A conicalshape, such as shown for example in FIG. 5, that allows for an expansionof the air/fuel mixture in the axially forward direction is preferred.The exemplary venturi 500 shown in FIG. 5 has an axially forward portion509 having an axially forward end 501, and an axially aft portion 511having an axially aft end 519. The axially forward portion 509 has agenerally cylindrical exterior shape (see FIG. 6) wherein the annularventuri wall 502 is generally cylindrical around the swirler axis 11.The venturi wall 502 has at least one groove 504 located on its radiallyexterior side capable of receiving a brazing material during assembly ofa nozzle tip assembly 68. In the exemplary embodiment shown in FIGS. 5and 6, two annular grooves 504 are shown, one groove 504 near theaxially forward end 501 and another groove 504 near an intermediatelocation between the axially forward end 501 and the axially aft end519. The grooves 504 may be formed using conventional machining methods.Alternatively, the grooves 504 may be formed integrally when the venturiwall 502 is formed, such as, for example, using the methods ofmanufacturing a unitary venturi 500 as described subsequently herein. Inanother aspect of the present invention, the venturi 500 comprises a lip518 (alternatively referred to herein as a drip-lip 518) located at theaxially aft end 519 of the venturi wall 502. The drip-lip 518 has ageometry (see FIG. 5) such that liquid fuel particles that flow alongthe inner surface 503 of the venturi wall 502 separate from the wall 502and continue to flow axially aft. The drip-lip 518 thus serves toprevent the fuel from flowing radially outwards along the venturi wallsat exit.

As shown in FIG. 5, the exemplary embodiment of venturi 500 comprises anannular splitter 530 having an annular splitter wall 532 locatedradially inward from the annular venturi wall 502 and coaxially locatedwith it around the swirler axis 1 1. The radially outer surface 533 ofthe splitter 530 and the radially inner surface 503 of the venturi wall502 form an annular swirled-air passage 534. The forward portion of thesplitter wall 532 has a recess 535 that facilitates interfacing theventuri 500 with an adjacent component, such as for example, shown asitem 208 in FIG. 2, during assembly of a fuel nozzle tip assembly 68.The splitter 530 has a splitter cavity 560 wherein a portion of the air190 mixes with the fuel ejected from the pilot outlets 162, 164 (seeFIG. 2).

The exemplary embodiment of the venturi 500 shown in FIGS. 5, 6 and 7comprises a swirler 510. Although the swirler 510 is shown in FIG. 5 asbeing located at the axially forward portion 509 of the venturi 500, inother alternative embodiments of the present invention, it may belocated at other axial locations within the venturi 500. The swirler 510comprises a plurality of vanes 508 that extend radially inward betweenthe venturi wall 502 and the annular splitter 530. The plurality ofvanes 508 are arranged in the circumferential direction around theswirler axis 11.

Referring to FIGS. 5 and 6, in the exemplary embodiment of the swirler510 shown therein, each vane 508 has a root portion 520 located radiallynear the splitter 530 and a tip portion 521 that is located radiallynear the venturi wall 502. Each vane 508 has a leading edge 512 and atrailing edge 514 that extend between the root portion 520 and the tipportion 521. The vanes 508 have a suitable shape, such as, for example,an airfoil shape, between the leading edge 512 and the trailing edge514. Circumferentially adjacent vanes 508 form a flow passage forpassing air, such as the CDP air shown as item 190 in FIG. 2, thatenters the swirler 510. The vanes 208 can be inclined both radially andaxially relative to the swirler axis 11 to impart a rotational componentof motion to the incoming air 190 that enters the swirler 510. Theseinclined vanes 508 cause the air 190 to swirl in a generally helicalmanner within venturi 500. In one aspect of the present invention, thevane 508 has a fillet 526 that extends between the root portion 520 ofthe vane 508 and the splitter wall 532. In addition to facilitatingreduction of stress concentrations in the root portion 510, the fillet526 also facilitates a smooth flow of air within the swirler and in theswirled air passage 534. The fillet 526 has a smooth contour shape 527that is designed to promote the smooth flow of air in the swirler. Thecontour shapes and orientations for a particular vane 508 are designedusing known methods of fluid flow analysis. Fillets similar to fillets526 having suitable fillet contours may also be used between the tipportion 521 of the vane 508 and the venturi wall 502. In the exemplaryembodiment of the venturi 500 shown in FIGS. 3-7 herein, the vanes 508are supported near both the root portion 520 and the tip portion 521. Itis also possible, in some alternative venturi designs, to have a swirlercomprising vanes having a cantilever-type of support, wherein a vane isstructurally supported at only one end, with the other end essentiallyfree. The venturi 500 may be manufactured from known materials that canoperate in high temperature environments, such as, for example, nickelor cobalt based super alloys, such as CoCr, HS188, N2 and N5.

The venturi 500 comprises a heat shield 540 for protecting venturi andother components in the fuel nozzle tip assembly 68 (see FIG. 3) fromthe flames and heat from ignition of the fuel/air mixture in a fuelnozzle 100. The exemplary heat shield 540 shown in FIGS. 5-7 has anannular shape around the swirler axis 11 and is located axially aft fromthe swirler 510, near the axially aft end 519 of the venturi 500. Theheat shield 540 has an annular wall 542 that extends in a radiallyoutward direction from the swirler axis 11. The annular wall 542protects venturi 500 and other components in the fuel nozzle tipassembly 68 from the flames and heat from ignition of the fuel/airmixture, having temperatures in the range of 2500 Deg. F to 4000 Deg. F.The heat shield 540 is made from a suitable material that can withstandhigh temperatures. Materials such as, for example, CoCr, HS188, N2 andN5 may be used. In the exemplary embodiments shown herein, the heatshield 540 is made from CoCr material, and has a thickness between 0.030inches and 0.060 inches. It is possible, in other embodiments of thepresent invention, that the heat shield 540 may be manufactured from amaterial that is different from the other portions the venturi, such asthe venturi wall 502 or the swirler 510.

The exemplary venturi 500 shown in FIGS. 5-7 has certain design featuresthat enhance the cooling of the heat shield 540 to reduce its operatingtemperatures. The exemplary venturi 500 comprises at least one slot 544extending between the venturi wall 502 and the heat shield 540. Thepreferred exemplary embodiment of the venturi 500, shown in FIG. 6,comprises a plurality of slots 544 extending between the venturi wall502 and the heat shield 540 wherein the slots 544 are arrangedcircumferentially around the swirler axis 11. The slots 544 provide anexit passage for cooling air that flows through the cavity between thefuel conduit and the venturi wall 502 (See FIG. 3). The cooling airentering the axially oriented portion of each slot 544 (see FIG. 3, 5)is redirected in the radially oriented portion of the slot 544 (see FIG.3, 5) to exit from the slots 544 in a generally radial direction ontothe side of the annular wall 542 of the heat shield. In another aspectof the present invention, the exemplary venturi 500 comprises aplurality of bumps 546 located on the heat shield 540 and arrangedcircumferentially on the axially forward side of the heat shield wall542 around the swirler axis 11. These bumps 546 provide additional heattransfer area and increase the heat transfer from the heat shield 540 tothe cooling air directed towards, thereby reducing the operatingtemperatures of the heat shield 540. In the exemplary embodiment shownin FIG. 6, the bumps 546 are arranged in four circumferential rows, witheach row having between 100 and 120 bumps.

An alternative exemplary embodiment of the present invention of aventuri is shown in FIG. 8. FIG. 8 is an isometric view of thealternative exemplary venturi 600 with a portion sectioned away.Referring to FIGS. 3 and 6, it is apparent to those skilled in the artthat the airflow entering the swirler 510 of the venturi 500, in somecases, may not be uniform in the circumferential direction when itenters passages between the vanes 508. This non-uniformity is furtherenhanced by the presence of other features, such as, for example, thewall 260 (see FIG. 3). In conventional venturis, such non-uniformity ofthe flow may cause non-uniformities in the mixing of fuel and air in theventuri and lead to non-uniform combustion temperatures. In one aspectof the present invention of a venturi 600 (see FIG. 8), the adverseeffects of circumferentially non-uniform flow entry can be minimized byhaving a swirler 610 comprising swirler vanes 609 with geometries thatare different from those of circumferentially adjacent vanes 608.Customized swirler vane 608, 609 geometries can be selected for eachcircumferential location based on known fluid flow analyticaltechniques. In the alternative exemplary embodiment of the presentinvention shown in FIG. 8, the vane 609 has an axial recess 635 forsuitably receiving an air flow that has been altered locally, such as,for example, due to the presence of a wall 260 in an adjacent componentin a fuel nozzle assembly tip 68 (see FIG. 3). The alternativeembodiment of the venturi 600 further comprises a heat shield 640,splitter 630, venturi wall 602, and other features as describedpreviously herein for the exemplary venturi 500. A venturi 600 havingswirlers with different geometries for the vanes 608, 609 located atdifferent circumferential locations can have a unitary construction andmade using the methods of manufacture described herein.

The exemplary embodiments of the unitary venturi 500 shown in FIGS. 5-7,and the alternative embodiments of the unitary venturi 600 shown in FIG.8, can be made using rapid manufacturing processes such as Direct MetalLaser Sintering (DMLS), Laser Net Shape Manufacturing (LNSM), electronbeam sintering and other known processes in the manufacturing. DMLS is apreferred method of manufacturing unitary venturis 500, 600 describedherein.

FIG. 9 is a flow chart illustrating an exemplary embodiment of a method700 for fabricating unitary venturis, such as items 500 and 600described herein, and shown in FIGS. 3-8. Although the method offabrication 700 is described below using unitary venturi 500 as anexample, the same methods, steps, procedures, etc. apply for thealternative exemplary embodiment of the venturi 600 shown in FIG. 8.Method 700 includes fabricating unitary venturi 500 (shown in FIGS. 3-7)using Direct Metal Laser Sintering (DMLS). DMLS is a known manufacturingprocess that fabricates metal components using three-dimensionalinformation, for example a three-dimensional computer model, of thecomponent. The three-dimensional information is converted into aplurality of slices, each slice defining a cross section of thecomponent for a predetermined height of the slice. The component is then“built-up” slice by slice, or layer by layer, until finished. Each layerof the component is formed by fusing a metallic powder using a laser.

Accordingly, method 700 includes the step 705 of determiningthree-dimensional information of a unitary venturi 500 and the step 710of converting the three-dimensional information into a plurality ofslices that each define a cross-sectional layer of the unitary venturi500. The unitary venturi 500 is then fabricated using DMLS, or morespecifically each layer is successively formed in step 715 by fusing ametallic powder using laser energy. Each layer has a size between about0.0005 inches and about 0.001 inches. Unitary venturi 500 may befabricated using any suitable laser sintering machine. Examples ofsuitable laser sintering machines include, but are not limited to, anEOSINT.®. M 270 DMLS machine, a PHENIX PM250 machine, and/or anEOSINT.®. M 250 Xtended DMLS machine, available from EOS of NorthAmerica, Inc. of Novi, Mich. The metallic powder used to fabricateunitary venturi 500 is preferably a powder including cobalt chromium,but may be any other suitable metallic powder, such as, but not limitedto, HS188 and INCO625. The metallic powder can have a particle size ofbetween about 10 microns and 74 microns, preferably between about 15microns and about 30 microns.

Although the methods of manufacturing unitary venturi 500 have beendescribed herein using DMLS as the preferred method, those skilled inthe art of manufacturing will recognize that any other suitable rapidmanufacturing methods using layer-by-layer construction or additivefabrication can also be used. These alternative rapid manufacturingmethods include, but not limited to, Selective Laser Sintering (SLS), 3Dprinting, such as by inkjets and laserjets, Sterolithography (SLS),Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS),Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), LaserNet Shape Manufacturing (LNSM) and Direct Metal Deposition (DMD).

The unitary venturi 500 for a fuel nozzle 100 in a turbine engine (seeFIGS. 1-3) comprises fewer components and joints than known venturis,swirlers and fuel nozzles. Specifically, the above described unitaryventuri 500 requires fewer components because of the use of a one-pieceunitary venturi 500 comprising a swirler 510 having a plurality of vanes508, a venturi wall 502 and a heat shield 540. As a result, thedescribed unitary venturi 500 provides a lighter, less costlyalternative to known venturis. Moreover, the described unitaryconstruction for the unitary venturi 500 provides fewer opportunitiesfor leakage or failure and is more easily repairable compared to knownventuris.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralsaid elements or steps, unless such exclusion is explicitly recited.When introducing elements/components/steps etc. of unitary venturi 500,600 described and/or illustrated herein, the articles “a”, “an”, “the”and “said” are intended to mean that there are one or more of theelement(s)/component(s)/etc. The terms “comprising”, “including” and“having” are intended to be inclusive and mean that there may beadditional element(s)/component(s)/etc. other than the listedelement(s)/component(s)/etc. Furthermore, references to “one embodiment”of the present invention are not intended to be interpreted as excludingthe existence of additional embodiments that also incorporate therecited features.

Although the methods and articles such as unitary venturi 500, 600described herein are described in the context of swirling of air formixing liquid fuel with air in fuel nozzles in a turbine engine, it isunderstood that the unitary venturi 500, 600 and methods of theirmanufacture described herein are not limited to fuel nozzles or turbineengines. The unitary venturi 500, 600 illustrated in the figuresincluded herein are not limited to the specific embodiments describedherein, but rather, these can be utilized independently and separatelyfrom other components described herein.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. The patentable scope of the inventionis defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

1. A venturi comprising: an annular venturi wall; a mixing cavitysurrounded circumferentially by the annular wall; and a swirler having aplurality of vanes arranged circumferentially around a swirler axis,wherein the swirler and the annular venturi wall have a unitaryconstruction.
 2. A venturi according to claim 1 wherein the swirler islocated at an axially forward end of the venturi.
 3. A venturi accordingto claim 1 further comprising an annular splitter located radiallyinward from the annular venturi wall.
 4. A venturi according to claim 3wherein the plurality of vanes extend between the venturi wall and theannular splitter.
 5. A venturi according to claim 3 wherein the splittercomprises an annular splitter wall coaxially located around the swirleraxis.
 6. A venturi according to claim 3 further comprising an annularswirled-air passage between an outer surface of the splitter and aninner surface of the venturi.
 7. A venturi according to claim 1 whereineach vane has a leading edge and a trailing edge located axially forwardfrom the leading edge, and has an orientation that facilitates producinga swirling motion to an airflow flowing through the swirler.
 8. Aventuri according to claim 1 wherein each vane has substantially thesame geometry.
 9. A venturi according to claim 1 wherein at least onevane has a geometry that is different from another vane.
 10. A venturiaccording to claim 1 further comprising a fillet between a root portionof a vane and the splitter.
 11. A venturi according to claim 10 whereinthe fillet has a contour that facilitates a smooth flow of air in theswirler.
 12. A venturi according to claim 5 wherein the splitter wallhas a recess that facilitates interfacing the venturi with an adjacentcomponent during assembly.
 13. A venturi according to claim 1 furthercomprising at least one groove located on the venturi wall capable ofreceiving a brazing material.
 14. A venturi according to claim 1 furthercomprising a lip located at an axially aft end of the venturi.
 15. Aventuri comprising: an annular venturi wall; a swirler located at anaxially forward portion of the venturi, the swirler having a pluralityof vanes arranged circumferentially around a swirler axis; and a heatshield located axially aft from the swirler, wherein the annular venturiwall, the swirler and the heat shield have a unitary construction.
 16. Aventuri according to claim 15 wherein the heat shield is annular.
 17. Aventuri according to claim 15 wherein the heat shield is located at anaxially aft end of the venturi.
 18. A venturi according to claim 16further comprising at least one slot extending between the venturi walland the heat shield.
 19. A venturi according to claim 16, furthercomprising a plurality of slots extending between the venturi wall andthe heat shield, the slots being arranged circumferentially around theswirler axis.
 20. A venturi according to claim 16, further comprising aplurality of bumps located on the heat shield and arrangedcircumferentially around the swirler axis.
 21. A venturi according toclaim 16, further comprising a lip located at the axially aft end of theventuri wall.